1. Field of the Invention
The present invention relates to a signal processing apparatus and, more specifically, relates to a signal processing apparatus which performs repeatedly the same processing for respective output channels in a time sharing fashion.
2. Description of the Related Art
In recent, a signal processing unit is known which performs operation on an input signal in accordance with a predetermined algorithm, and which is used as a sound source and an effector in an electronic musical instrument, and further is used in a wide variety of appliances such as audio equipments and communication equipments. The signal processing unit used in these appliances is required to process a number of data in a very short time. Such operation includes multiplication, addition, subtraction, Laplace transform, etc. And the input data to be processed by the signal processing unit are of large bits. Therefore, it is not efficient and economical to provide the signal processing unit with separate and independent operational elements prepared for respective operations.
Hence, another signal processing unit is proposed in which a single operational element performs various operation in a time sharing fashion in accordance with a micro-program stored within the signal processing unit.
More recently, however, an electronic musical instrument involves multi-channels so as to generate a plurality of musical tones at the same time while a communication system of multi-channels simultaneously transmits signals to a plurality of receivers. The signal processing apparatus employed in the multi-channel musical instrument and multi-channel communication system are arranged to receive signals for respective channels in a time sharing fashion and to sequentially perform operation on the signals received in a time sharing fashion.
Since the multi-channel signal processing apparatus performs operation for each channel, it requires substantially similar programs for respective channels, resulting in including a large storage capacity for storing these programs.
Some multi-channel signal processing apparatus holds a program for one channel as a sub-routine program and reads out the sub-routine program every time when it executes processing for each channel. In such multi-channel signal processing apparatus, however, a stack area is needed for program counter under an instruction of a sub-routine jump and there is a disadvantage that the time to execute the jump instruction reduces the net time for performing other operation.